Moon Hae Kim

A middleware model supporting time-triggered message-triggered objects for standard Linux systems

Abstract The Time-triggered Message-triggered Object (TMO) programming and specification scheme came out of an effort to remove the limitations of conventional object structuring techniques in developing real-time (RT) distributed computing components and composing distributed computing applications out of such components and others. It is a natural and syntactically small but semantically powerful extension of the object oriented (OO) design and implementation techniques which allows the system designer to specify in natural and yet precise forms timing requirements imposed on data and function components of high-level distributed computing objects. TMO Support Middleware (TMOSM) was devised to be an efficient middleware architecture that can be easily adapted to many commercial-off-the-shelf (COTS) hardware + kernel operating system platforms to form efficient TMO execution engines. However, up until 2003, its adaptations were done for Microsoft Windows platforms only. As we have been developing and refining an adaptation of TMOSM to the Linux 2.6 operating system platform in recent years, TMOSM has been refined to possess further improved modularity and portability. This paper presents the refined TMOSM as well as the techniques developed for efficient adaptation of TMOSM to the Linux 2.6 platform.

Scalable packet classification through rulebase partitioning using the maximum entropy hashing

In this paper, we introduce a new packet classification algorithm, which can substantially improve the performance of a classifier. The algorithm is built on the observation that a given packet matches only a few rules even in large classifiers, which suggests that most of rules are independent in any given rulebase. The algorithm hierarchically partitions the rulebase into smaller independent subrulebases based on hashing. By using the same hash key used in the partitioning a classifier only needs to look up the relevant subrulebase to which an incoming packet belongs. For an optimal partitioning of rulebases, we apply the notion of maximum entropy to the hash key selection. We performed the detailed simulations of our proposed algorithm on synthetic rulebases of size 1 K to 500 K entries using real-life packet traces. The results show that the algorithm can significantly outperform existing classifiers by reducing the size of a rulebase by more than four orders of magnitude with just two-levels of partitioning. Both the time complexity and the space complexity of the algorithm exhibit linearity in terms of the size of a rulebase. This suggests that the algorithm can be a good scalable solution for medium to large rulebases.

TMO-eCos: an eCos-based real-time micro operating system supporting execution of a TMO structured program

The TMO (time-triggered message-triggered object) model is a well-known real-time object model for distributed and timeliness-guaranteed computing. A couple of years ago, we developed a Linux-based real-time kernel supporting execution of a TMO structured program, named TMO-Linux. TMO-Linux has been used well in various applications including small embedded devices and real-time control applications, but it still has some drawbacks due to its size and server-like characteristics. To overcome these problems, we recently developed a small embedded kernel to support execution of a TMO structured program by modifying eCos/spl trade/ kernel named TMO-eCos. TMO-eCos supports a deadline-driven scheduling, a network transparent distributed IPC, and time-triggered and message-triggered real-time threads for TMO-based OO programming. In this paper, we present the design of TMO-eCos.

Demand-driven curriculum for embedded system software in Korea

This paper describes how Korean Government has designed and driven the innovation of undergraduate curriculums to meet increasing industrial demand for quality IT experts in the computer-software field. The computer-software field has been categorized into five specialized areas, tracks. The embedded system software area is one among them. Educational contents (including track curriculums, detailed syllabuses, and class materials) have been designed and constructed for the tracks. First, a curriculum development methodology is described, which is used to develop curriculums in the computer-software field. Next, artifacts for the embedded software system track produced in the process are described. By applying iterative and incremental principles of the methodology, all artifacts will be continuously updated and constantly upgraded as related technologies progress rapidly.

A Cluster-Based TMO-Structured Scalable Approach for Location Information Systems

Location-based service (LBS) systems have recently become a subject of active research and development. A key issue in such systems is efficient management of current and past location information of moving items. In the past two years, we have been establishing a new LBS system architecture, named the GALIS (Gracefully Aging Location Information System), which is based on the new approach of using a cluster of database server nodes and effecting efficient distributed and parallel computing in both real-time update of location records of moving items and processing of location-related queries. Each server node is dedicated to keeping records relevant to a different geographical zone and a different temporal zone. Each subsystem in GALIS is structured as a TMO network for the sake of easy analysis and expansion. A prototype implementation of GALIS has been realized only partially, and its full implementation is under way. In this paper, major features of GALIS are presented together with discussions on trade-off considerations which led to the adoption of those features. Issues remaining for further research are also briefly discussed.

Time-triggered message-triggered object modeling of a distributed real-time control application for its real-time simulation

The time-triggered message-triggered object (TMO) has been devised as the basic component model for high level distributed real time programming as well as real time application system/subsystem design and modeling. One of the strengths of the TMO is its facilitation of multi-phased top-down modeling of real time distributed computing application systems. TMO-structured models are capable of representing both a real time control system and its controlled facilities (composed of sensors, actuators, and monitored infrastructure) in a uniform fashion. Also, TMO-structured real time simulation models can be generated in attractively simple forms and they can be executed to enable examination of not only the logical accuracy of a real time control system being developed but also the correctness of its timing behavior. A case study of such simulation modeling has been conducted in the context of constructing a real time simulator of a real time control system called the safety injection system (SIS) which is a subsystem of a nuclear power plant. In the course of this case study, some tools that support efficient real time simulation have been developed. The refined modeling steps, the support tools developed, and the cost-effectiveness confirmed in the course of this case study are the main subjects discussed.

Issues in realization of an execution time analyzer for distributed real-time objects

An issue that the real-time software research community has long recognized as an important technological challenge but has not shown much progress in meeting the challenge is to guarantee response times of real-time distributed systems. Two basic problems must be addressed to effectively meet this challenge: establishment of the distributed real-time program structure and the system infrastructure structure that enable systematic analysis of the worst-case time behavior of the application systems; and development of tools which perform automated analysis of the worst-case time behavior while leaving only minimal work to the designers. Research on the first problems has produced some useful results in recent years. Time is thus ripe for tackling the second problem on the basis of those recent developments in handling the first problem. This paper describes a desirable systematic timing analysis process which builds upon the recent results in the first problem area. An outline of a desirable analysis tool is also presented.

A real-time mobile GIS based on the HBR-tree for location based services

Recently, as the growth of the wireless Internet, PDA, and HPC, the focus of research and development has been changed to LBS (location based service). To offer LBS efficiently, there must be a real-time GIS platform that can deal with dynamic status of moving objects and a location index which can deal with the characteristics of location data. Therefore, in this paper, we studied the real-time mobile GIS based on the HBR-tree to manage mass of location data efficiently. The real-time mobile GIS mainly consists of the HBR (Hash Based R)-tree and the real-time GIS platform. The HBR-tree is a combined index type of the R-tree and the spatial hash index. Although location data are updated frequently, update operations are done within the same hash table in the HBR-tree, so it costs less than other tree-based indexes. The real-time GIS platform consists of a real-time GIS engine, a middleware, and a mobile client.

Distributed scalable location data management system based on the GALIS architecture

A challenging task in the LBS system engineering is to implement a highly scalable system architecture which can manage moderate-size configurations handling thousands of moving items as well as upper-end configurations handling millions of moving items. The architecture named the GALIS is a cluster-based distributed computing system architecture that consists of multiple data processors, each dedicated to keeping records relevant to a different geographical zone and a different time zone. In this paper, we explain a prototype location data management system structuring major components of GALIS by employing the TMO programming scheme, including the execution engine middleware developed to support real-time distributed object programming and real-time distributed computing system design. We present how to generate realistic location sensing reports and how to process such location reports and location-related queries. Some experimental results showing performance factors regarding distributed query processing are also explained.

TMO-structured cluster-based real-time management of location data on massive volume of moving items

A major challenge in the field of location based service (LBS) system engineering, is to establish a highly scalable system architecture which can be instantiated in moderate-size configurations handling thousands of moving items as well as in upper-end configurations handling millions of moving items. We are exploring an approach of using a cluster of database server nodes and effecting efficient distributed and parallel computing in both real-time update of location records of moving items and processing of location-related queries. The approach of developing efficient middleware which is layered on a cluster of nodes running commercial off-the-shelf database servers, has been adopted. The middleware design is substantially based on the TMO scheme for real-time distributed object programming and real-time distributed computing system design, which enables low-overhead coordination of distributed computations and highly abstract distributed programming styles.